This invention relates to a picture signal converting device and is more particularly related to such a device used for converting a picture taken by a video camera into a movie film image.
An electron beam recorder (EBR) is a conventional picture signal converting device used for forming a picture taken by a video camera on a movie film.
Specifically, as illustrated in FIG. 1, a picture signal converting device 1 temporarily records a video picture signal VD1 obtained from a video camera 2 in a recording VTR 3 and thereafter slow-reproduces this signal by use of a subsequent slow reproducing VTR 4 to provide a low speed video signal VD2. The signal VD2 is then inputted to an EBR device 5.
The EBR device 5 includes a picture signal converting circuit 6 which performs predetermined signal processing on a video picture signal VD2. The picture signal converting circuit unit 6 generates a film recording signal VD3 by sequentially and intermittently outputting the red, green, and blue components of each frame of picture data. The signal VD3 is inputted to a beam gun 8 included in a subsequent EBR unit 15.
The beam gun 8 scans an electron beam BM on a black-and-white film 9 while modulating the intensity of the electron beam BM with the film recording signal VD3. Only the respective contrast of the color components in the film recording signal VD3 is formed on the black-and-white film 9.
As illustrated in FIG. 2, the picture formed on the black-and-white film 9 is sequentially allocated to one frame for each of the red, green, and blue components of each frame of picture data intermittently outputted from the picture signal converting circuit unit 6.
In particular, the EBR unit 15 records the contrast of the red component of the film recording signal VD3 in a first recording area of the black-and-white film 9, thereby forming the contrast picture FR1 corresponding to the red component. The black-and-white film 9 is then fed forward by one frame and temporarily stopped. The contrast of the green component of the recording signal VD3 is recorded in a subsequent second recording area, thereby forming the contrast picture FG1 corresponding to the green component. The black-and-white film 9 is again fed forward by one frame and temporarily stopped. The contrast of the blue component of the recording signal VD3 is recorded in a subsequent third recording area, thereby forming the blue component picture FB1.
In this manner, the respective contrast pictures FR1, FG1, and FB1 for the red, green, and blue components of the reproducing picture outputted from the slow reproducing VTR 4 are sequentially formed in order on the black-and-white film 9.
Next, using the contrast pictures FR1, FG1, and FB1 of the respective primary color components which are formed on the black-and-white film 9, the red component contrast picture FR1 is recorded in a first recording area of a color negative film 11 through the red subfilter R of a filter 10, while the green component contrast picture FG1 is also recorded in the first recording area of the color negative film 11 through the green subfilter G of the filter 10, and the blue component contrast picture is also recorded in the first recording area of the color negative film 11 but through the blue subfilter B of the filter 10. A color negative picture FCOLN synthesized with the red, green, and blue components is thereby formed on the first recording area of the color negative film 11.
Finally, the picture of the color negative film 11 is transferred on to a color positive film 12, which is then usable as a movie film.
In this type of picture signal converting apparatus 1, the dynamic range from the black level to the white level of the video signal is narrower than the dynamic range of the film. Therefore, the red, green and blue components of the video signal which have a narrow dynamic range, are level converted using a gamma correcting circuit composed of a non-linear circuit, to spread the range from the black level to the white level and to match the video signal with the tone characteristics of the film. There is a problem with this type of processing in that the tone, chrominance and brightness of color of the pictures may change.
Conversion of the video signals with high-fidelity is especially difficult when the picture is monochromatic, because the color is darkened due to reduction of the chrominance and brightness.
The video picture signal VD1 outputted from the video camera also is corrected within the camera so as to match the gamma characteristic of the color phosphors of a CRT (cathode ray tube) so that a natural-appearing picture is displayed by the CRT from a video picture signal supplied directly from the camera (this correction being sometimes referred to as the "camera gamma characteristic"). The input picture provided for imaging by the video camera 2 is not linearly related to the picture signal outputted from the video camera.
In the picture signal converting apparatus 1 using an EBR unit, it is also necessary to correct the signal VD1 to match the gamma characteristic of the film on which the signal VD1 is to be recorded.
Therefore, in the picture signal converting circuit unit 6, the video picture signal VD2 is gamma corrected to match the gamma characteristic of the film.
This gamma correction is carried out by simultaneously correcting for the camera gamma characteristic and matching the gamma characteristic of the film. To do so, it is necessary to provide a correction curve that has both a correcting characteristic based on the camera gamma characteristic and a correcting characteristic based on the gamma characteristic of the film.
However, simultaneous correction with respect to both the camera gamma characteristic and the film gamma characteristic makes it complicated to provide a correcting characteristic which matches both the camera gamma characteristic and the film gamma characteristic. In addition, if either one of the video camera or the film is changed, the correcting characteristic must be redetermined. As a result, there are restrictions on selection of the video camera and the film.
Moreover, in the method described above in which a picture is formed on a black-and-white film 9 using an electron beam BM, the recording is performed by reducing the scanning speed of the electron beam BM to match the characteristics of the film so that the picture is formed with very high resolution.
Accordingly, a slow-reproduced picture is obtained by recording the video picture signals VD1 with the recording VTR 3 at a predetermined recording speed, reproducing the recorded signals with slow reproducing VTR 4 and repeatedly outputting the same frame thirty times per second. Then two repetitions are selected from the thirty repeated pictures and undergo timebase conversion, so that the speed is reduced down to the predetermined signal speed. The resulting film recording signals are used to form the picture with very high resolution on the black-and-white film 9.
Further, when the contrast pictures FR1, FG1, and FB1 for the respect primary color components are formed on the black-and-white film 9, the black-and-white film 9 is repeatedly stopped and fed. During this process, the red, green, and blue components of the film recording signals VD3 must be sequentially and intermittently transmitted.
As a result, the slow intermittent film recording signals VD3 can not be displayed using a monitor device adapted to receive normal video picture signals. To determine whether or not the picture signal converting device 1 is operating correctly and the desired picture is being formed on the film, it has been necessary to wait until the film was developed.
Specifically, in the EBR device 5 various kinds of signal processing such as color correction processing to correct color deviation of the video picture signal VD1, gamma processing to match gamma characteristics with the film characteristics, etc. are performed, and proper execution of these processes must be supervised. Detection of defects on the developed film, so that EBR recording must be re-effected, and other causes, have resulted in reduced operating efficiency.
In addition, during production of a movie film with editing by selecting predetermined scenes from the video picture signals VD1 for recording on the film, if the signals being recorded on the film can be directly monitored, the efficiency of the editing operation can be improved.